Collective state transitions of exciton-polaritons loaded into a periodic potential

TL;DR

This paper investigates how exciton-polaritons, as composite bosons in a dissipative system, transition between different energy states within a periodic potential, revealing controlled loading mechanisms and the role of fluctuations and phonon scattering.

Contribution

It demonstrates controlled loading of polaritons into specific energy bands in a periodic potential and models the nonequilibrium condensation process including quantum and thermal fluctuations.

Findings

Observation of transition from incoherent Bose gas to polariton condensate

Controlled loading into distinct energy bands by shaping excitation beams

Identification of polariton-phonon scattering as key relaxation mechanism

Abstract

We study the loading of a nonequilibrium, dissipative system of composite bosons -- exciton polaritons -- into a one dimensional periodic lattice potential. Utilizing momentum resolved photoluminescence spectroscopy, we observe a transition between an incoherent Bose gas and a polariton condensate, which undergoes further transitions between different energy states in the band-gap spectrum of the periodic potential with increasing pumping power. We demonstrate controlled loading into distinct energy bands by modifying the size and shape of the excitation beam. The observed effects are comprehensively described in the framework of a nonequilibrium model of polariton condensation. In particular, we implement a stochastic treatment of quantum and thermal fluctuations in the system and confirm that polariton-phonon scattering is a key energy relaxation mechanism enabling transitions from the highly nonequilibrium polariton condensate in the gap to the ground band condensation for large pump powers.